Linear actuator design idea

Been working on this design for a couple days.

I'm looking at fixing the outer cover at the top and bottom with screws, instead of running 2-4 rods the length of the cover and fixing at the top and bottom.
Can anyone see a reason this might not work ?

Also planning on making the top piston bearing/bush out of a molybdenum infused plastic, instead of using a linear bearing or Igus bush.

Here are a couple pictures of the design. (Please excuse the CAD skills. I know my way around, but am no expert).

Any feedback welcomed!

Cheers
Jamie

The screws to fix the cylinder, will have to endure searing forces from the piston rod trying to rotate, plus the load can cause them to sear if for any reason the actuators get in bind and not aligned... no matter how hard is the tap, its not going to be tight enough to make the cylinder rigid compared to the motor.

What motor is that anyway? Why you need support rods for it all the way to its back (usually the encoder department of servos)?

Hi Thanos,

I was basing my design on Petertje's build.
https://www.xsimulator.net/community/threads/hexapod-racing-sim.14693/

The piston attachment joint doesn't rotate. Using the same design each end of the actuator as per Petertie's build again.
The piston is 50mm stainless with a wall of 1.6mm

The motor is a 750watt 80st AC.
Ballscrew 1610 600mm

Cheers
Jamie

consider a belt from the motor to the ballscrew so you can adjust the gear ratio if needed

also think about materials to reduce noise

Thanks Gadget999,

That would take a little more design work. But good idea.
The 1610 ballscrew should be fast, provided the motor can deliver the torque. I guess it will depend on the platform weight to a large degree.
Would be nice to be able to trade a little speed for torque if needed, with belts and gearing.

I'm planning on using a material called Nylatron for the top bush/bearing. Very low wear and should be much quieter than a linear ball bearing.

Hi Jamie, I just had a closer look to your design and I think you should change two details:

The first is, you really should add a piston as a guidance for the ballscrew-nut. There are some reasons for this:
1. even small side forces will increase the friction dramatically on the upper linear bearing and block the movement more or less.
2. The ballscrew tends to wobble at higher speed and needs exact guidance on the lower and upper side.

The second detail is the guidance of the upper side of the ballscrew. In your design it is a thin (10-12mm?) disc that could block when it will tilt a little (mechanical drawer effect).

Wickie

Hi Wickie,

Thanks for your advice.

Do you mean a ring between the outside of the piston and the inside of the outer tube to support it from the bottom ? Sounds like a good idea, and wouldn't be hard to add.

Yes, the top ballscrew support is 10mm thick. This could also be easily doubled, I will look into that also.

Thanks again for your valuable input.

Cheers
Jamie

Hi Jamie,
I meant like this:

Thanks Wickie. That's what I thought you meant.
I have implemented it in my design now.